The invention relates to a pressure-volume delivery system comprising a piston-cylinder unit with a piston acting on both sides (dual-action reciprocating piston), said piston having at least two different active surfaces in corresponding pressure chambers and the pressure chambers being connected to at least one consumer via hydraulic lines. The delivery system also comprises a drive for the piston-cylinder unit. According to the invention, the pressure chambers and/or hydraulic lines are interconnected by means of at least one or more switching valves connected in parallel and having a large flow cross-section (AV) and via a short hydraulic line or lines with low flow resistance.
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23. A pressure-volume delivery system comprising:
a piston-cylinder unit with a piston acting on both sides, said piston having at least two active surfaces of different sizes, and wherein each active surface of the piston is associated with a respective pressure chamber of the piston, wherein the pressure chambers of the piston are connected via hydraulic lines with at least one consumer and with a drive for the piston-cylinder unit, and
a connecting line configured to connect the pressure chambers and/or the hydraulic lines, the connecting line having a short design and a sufficiently low flow resistance so as not to throttle flow, wherein the connecting line is configured with one or more switching valves, wherein in the case of multiple switching valves, the multiple switching valves are connected in parallel with each other, the one or more switching valves having a sufficiently large cross-flow section so as not to throttle flow when the one or more switching valves is/are open, wherein delivery capacity/pressure build-up of the piston-cylinder-unit is enabled to be varied by means of the switchable valve by varying switchable active surfaces in the forward stroke and the delivery unit being operated in forward and return strokes.
1. A pressure-volume delivery system comprising:
a piston-cylinder unit with a piston acting on both sides, said piston having at least two active surfaces of different sizes, and wherein each active surface of the piston is associated with a respective pressure chamber of the piston, wherein the pressure chambers of the piston are connected via hydraulic lines with at least one consumer, and the piston-cylinder unit also including a drive coupled to the piston and configured to drive the piston in a reciprocating manner, and
a connecting line configured to connect the pressure chambers and/or the hydraulic lines, the connecting line having a short design and a sufficiently low flow resistance so as not to throttle flow, wherein the connecting line is configured with one or more switching valves, wherein in the case of multiple switching valves, the multiple switching valves are connected in parallel with each other, the one or more switching valves having a sufficiently large cross-flow section so as not to throttle flow when the one or more switching valves is/are open,
wherein:
(a) the different sized active surfaces of the piston are in a ratio of between 1.5 and 1 to between 2.5 and 1, to each other,
and/or
(b) delivery capacity/pressure build-up of the piston-cylinder-unit is enabled to be varied by means of the switchable valve by varying switchable active surfaces in the forward stroke and the delivery unit being operated in forward and return strokes.
24. An activation system for a motor vehicle brake, the activation system comprising:
an activation device,
a piston-cylinder unit with a piston acting on both sides, said piston having at least two active surfaces of different sizes, and wherein each active surface of the piston is associated with a respective pressure chamber of the piston, wherein the pressure chambers of the piston are connected via hydraulic lines with a hydraulic brake circuit, to provide compressant to and pressurize the hydraulic brake circuit, and also including a drive coupled to the piston and configured to drive the piston in a reciprocating manner, and
a connecting line configured to connect the pressure chambers and/or the hydraulic lines, the connecting line having a short design and a sufficiently low flow resistance so as not to throttle flow, wherein the connecting line is configured with one or more switching valves, wherein in the case of multiple switching valves, the multiple switching valves are connected in parallel with each other, the one or more switching valves having a sufficiently large cross-flow section so as not to throttle flow when the one or more switching valves is/are open,
wherein:
(a) the different sized active surfaces of the piston are in a ratio of between 1.5 and 1 to between 2.5 and 1, to each other,
and/or
(b) delivery capacity/pressure build-up of the piston-cylinder-unit is enabled to be varied by means of the switchable valve by varying switchable active surfaces in the forward stroke and the delivery unit being operated in forward and return strokes.
2. The pressure-volume delivery system according to
3. The pressure-volume delivery system according to
4. The pressure-volume delivery system according to
5. The pressure-volume delivery system according to
non-return valves closing towards the reservoir arranged in the at least one hydraulic line connecting the pressure chambers with the reservoir.
6. The pressure-volume delivery system according to
7. The pressure-volume delivery system according to
8. The pressure-volume delivery system according to
9. The pressure-volume delivery system according to
10. The pressure-volume delivery system according to
11. The pressure-volume delivery system according to
12. The pressure-volume delivery system according to
13. The pressure-volume delivery system according to
14. A method for supplying pressure with a variable delivery rate and/or accurate pressure dosing, the method comprising using the pressure-volume-delivery system according to
15. The method according to
16. The method according to
17. The method according to
18. The method according to
19. The method according to
20. The method according to
21. The method according to
22. The method according to
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This application is a Section 371 U.S. National Stage Filing of International Application No. PCT/EP2014/069723, filed Sep. 16, 2014, which was published in the German language on Mar. 19, 2015, under International Publication No. WO 2015/036623 A2, which claims priority to German Patent Application No. 10 2013 110 188.7, filed on Sep. 16, 2013, and German Patent Application No. 10 2013 111 974.3, filed on Oct. 30, 2013, the disclosures of which are incorporated herein by reference.
The invention relates to an electrically-driven pressure regulator- and volume-delivery unit according to the preamble of Claim 1.
The prior art comprises piston or geared pumps, which are generally driven by combustion engines and deliver a volume flow in a fixed relationship to the speed of the combustion engine. Embodiments of pumps allowing a variable delivery capacity are axial piston pumps with adjustable swash plates, or variable vane pumps. For a demand-oriented delivery these pumps are electrically driven.
The abovementioned pumps are mechanically very expensive and complicated to build and because of relatively high leakage do not allow precise pressure regulation by motor positioning control.
Pumps are also known that are based on a dual-action reciprocating piston, delivering by means of a forward and backwards movement (bicycle pump principle). The dual-action reciprocating piston is connected via two non-return valves with a reservoir and via two further non-return valves with the consumer. Double stroke piston pumps in an electrically driven form are known from DE 10 2006 030 141.2. Such double stroke piston pumps are significantly simpler to build than axial piston pumps and vane pumps.
Finally, from DE 2011 080312 a braking system is known with a dual-action reciprocating piston driven by a linear actuator, in which in the hydraulic lines leading from the pressure chambers to the wheel brakes sequence valves are arranged, wherein the hydraulic lines can be connected via a supplementary valve.
A disadvantage of the design of the dual-action reciprocating piston from DE 2001 080312 is that the hydraulic connection between the front and back of the dual-action reciprocating piston passes through three valves, which have a major throttling effect. This makes rapid switching between forward and return stroke operation impossible. In addition, during the forward stroke it is impossible to switch to smaller active surfaces, since for such a function a more rapid pressure balance between the chambers is necessary. In DE 2011 0803212 it is simply the effect of the different cross sectional areas that is used to achieve a higher pressure in the return stroke (Claim 15). Dynamic switching between the forward and return stroke is not provided for in DE 2011 0803212, and in addition the reliability of the operating principle for use as a pump for forward and return stroke operation is low.
The object of the invention is to provide an electrically-driven pressure regulator- and volume-delivery unit with high delivery capacity and accurate and dynamic pressure control.
The object of the invention is achieved by the features of Claim 1.
With the achievement according to the invention a pressure regulator- and volume-delivery unit electrically driven by a linear actuator or a motor-transmission unit based on the dual-action reciprocating piston principle is provided, which can accurately build up pressure or deliver volume in a demand-oriented manner and allow rapid switching between differing hydraulically active surfaces. To this end, avoiding throttling losses is critical from a functional point of view.
This can be achieved by connecting the front and back of the dual-action reciprocating piston via switching valves having large flow cross-sections and a direct connection between the front and back via a short hydraulic line with low flow resistance, which in the area of the end stroke of the dual-action reciprocating piston connects the first chamber with the starting stroke of the dual-action reciprocating piston of the second chamber. The length of the connection is thus approximately as big as the entire stroke of the dual-action reciprocating piston. For a low-flow design the dual-action reciprocating piston and connecting line usefully form part of a hydraulic block, which connects the two chambers by bore holes. The switching valve is preferably also arranged in the hydraulic block. Alternatively, a plurality of valves can also be connected in parallel, in order to improve the flow resistance, or to allow the use of serially produced standard valves with small flow cross-section. The valves must also be designed for high differential pressures. By using just one valve or connecting valves in parallel rather than having three valves in series (DE 2011 0803212) the reliability of the dual-action reciprocating piston is also guaranteed in forward and return strokes. Should one of the three valves of DE 2011 0803212 fail, operation is no longer possible, but with the achievement according to the invention the reliability is very high and, in addition, by connecting the valves in parallel full functional redundancy can be achieved.
Furthermore, for the purposes of optimisation (downsizing of the linear actuator) the choice of cross-sectional areas between the front and back of the dual-action reciprocating piston is crucial. A ratio of the areas between the front and back of the dual-action reciprocating piston of 1.5 to 2.5, preferably 2 should be selected here, in order to achieve effective downsizing.
With the invention or its versions and further developments both variable delivery capacities and precise pressure control can be achieved or functionally represented.
In addition, with the achievement according to the invention in the forward stroke highly dynamic switching between two differing working cross-sections is possible. Since in many motor applications in vehicles an interruption in pressure build-up is functionally undesirable (in braking systems, for example, a build-up of pressure from 0 to 120 bar must be possible with no, or very few, interruptions), highly dynamic switching to a second active surface must take place. If this can be functionally implemented by connecting the two chambers of the dual-action reciprocating piston with low flow resistances, the smaller active cross-sectional surfaces can be used at high pressures in order to reduce the power/torque demand of the linear actuator at the forward stroke stage. This allows significant downsizing of the linear drive. A downsized linear actuator also has a low moving mass/inertial mass. This leads to further advantages when switching between forward and return strokes.
At higher pressures (primarily>40% of the maximum pressure) the dual-action reciprocating piston is operated in the forward and return strokes. In this operating mode both in the forward and return strokes smaller active hydraulic areas are in operation. The switching between forward and return strokes is highly dynamic. This control strategy can be applied for operation at high pressures, where small interruptions in the pressure build-up/flow rates through switching from forward stroke to return stroke operation can be tolerated. The low flow resistances in combination with the low moving mass/inertial mass of the linear actuator minimise the dead time during switching. As a result of the smaller active surfaces the torque requirement of the linear actuator is reduced and so the linear actuator can be operated at high rotational/linear speeds. Despite the linear actuator being smaller, as a result of the higher rotational speeds high flow rates or pressure build-up gradients can be achieved. In addition, the volume of the dual-action reciprocating piston unit can be significantly reduced, if delivery can take place in both the forward and return strokes.
Furthermore, accurate pressure control is functionally implemented via path control of a linear actuator both during pressure build-up and also optionally during pressure reduction. For this a pressure-volume (path) curve is mapped via a pressure sensor as a model and used for control.
Alternatively, to the linear actuator the dual-action reciprocating piston can also be operated via a motor-transmission solution. In this case, which is not described in more detail, a transmission is positioned between the motor and the dual-action piston connecting rod, which also allows a right-angled arrangement of the dual-action reciprocating piston relative to the motor.
The device according to the invention also allows one or more hydraulic consumers to be supplied highly efficiently with pressure and volume, and at the same time a guarantee of accurate control of the consumers. The main application is for hydraulic consumers in motor vehicles.
Advantageous configurations or further developments of the invention are contained in the other claims, to which reference is made here.
In other words, with the achievement according to the invention or its embodiments and further developments, inter alia the following functions can be provided or the following advantages achieved:
Thanks to the degree of freedom and accurate pressure control, switching of the valves of consumers can be simplified (e.g. replacement of costly proportional valves by simple solenoid valves), in addition the linear drive can be significantly simplified by the switchable active surfaces.
In a variant, two further switchable valves are used (
A number of consumers can be connected to the pressure regulator- and volume-delivery unit, which can be switched on and off via solenoid valves.
The invention is described in more detail in the drawing, using the figures below.
These show as follows:
The pressure regulator unit has connections to a consumer by means of two further non-return valves 6a and 6b, having a large cross-section and which during pressure build-up can be rapidly opened without electrical operation. The AV valves are thus under load only when switching between forward and return strokes, or switching the cross-sectional areas. For example, if the pressure regulator unit is used in a braking system (36 cm3 volume), when switching up to 100 bar typically a cross-section of the AV valve of approximately 5 mm2 is necessary. Typically, rapidly switching ball seat valves have a cross-section of 0.8-1.4 mm2. If pressure compensation has to take place via 2 valves (according to the prior art DE 2011 0803212), connection of the valves in series would require at least 4 times the cross-sectional area of the valves. If in addition account is taken of the fact that 4 lines connect the valves with corresponding flow and valve connection resistances to be considered, a further increase in the cross-sectional area is necessary and a rapid switching at high pressures is technically unfeasible. A rapid switching of such larger valves is technically very difficult to implement, and very expensive, and a hindrance to normal operation without switching. Such large valves switch very slowly and must be activated for each pressure/delivery operation, and are therefore under load for each change in pressure/volume and so in view of the large number of operations are not fail-safe. A failure of one valve leads to the loss of the switching function, which can result in a failure of the entire system, as sufficient volume for the pressure build-up is no longer available or the delivery has to be interrupted. Technically speaking, therefore, it is crucial for the AV valve to be arranged in front of the non-return valves 6a and 6b and the volume flow to the consumer to be delivered via non-return valves only. In addition, diagnostics on the AV-valve can be performed for each forward stroke and leakages can be identified early. In the connection a pressure sensor 7 is also arranged. The pressure regulator unit is driven by means of a motor-spindle drive. The motor-spindle drive has a ball screw drive 8 and a motor rotor 10 supported by two bearings 9a and 9b, and equipped with permanent magnets. The rotor speed and angular position are determined via a sensor 14. The motor also has a stator 11 with exciter coils 12 and is accommodated in a housing 13. Between chambers 3a and 3b seals D1 are arranged on the dual-action reciprocating piston 1 and between chamber 3b and active surface A2 and push-rod piston 2 seals D2 are arranged.
The dual-action reciprocating piston 1 can be operated in forward and return strokes. In the forward stroke when the valve AV is closed the surface A1 is active, and with the valve AV open the surface A2-A1, since a pressure compensation between the two chambers can take place. In the return stroke the valve AV is closed and surface A2 is active.
Advantageously, the ratio between the surface A1 and A2 is approximately a factor of 2, so that in the forward and return strokes the same small surface A2 can be used for control and during switching no compensating volume flows and pressure drops are active.
Switching to half the surface has the result that the motor torque can be designed for significantly lower maximum torques, leading to essential cost reductions for the drive unit. This is described in more detail in
This effect leads to significant cost advantages: use of a motor with low weight and costs and reduction in the load on the ball screw, both being significant costs for example in an electrical braking system. Performance can also be increased.
A relationship between the chamber surfaces of the dual-action reciprocating piston of A/A2=2 is taken as a basis in the representation. The pressure build-up commences from a starting pressure s0A1. A desired control pressure p1 is set by operating the linear actuator as far as Position Sp1. For the regulation the pressure-stroke curve is taken as a basis which reflects the nonlinear relationship between pressure and path. Lower pressures than p1 can also be applied via the pressure-path curve. When switching to the active surface A2 the pressure-volume curve shifts. The result is a new reference path s0A2. Pressure changes can be set by setting differential paths □sk. The path-controlled pressure control strategy has the advantage that the pressure can be adjusted significantly better if the control takes place by means of the stroke and not using the pressure sensor, since in this way pressure variations and elasticities in the pressure line do not affect the control as disturbance variables and high demands do not have to be placed on the accuracy of the pressure sensors.
If the pressure regulator unit according to
The pressure build-up takes place via the valves 22a and 21a with accurate pressure control via pressure-path curve, as a result of which for the operation of both systems only one pressure sensor is necessary. The pressure reduction takes place via timing control of the pressure relief valves 21b and 22b, wherein the relief valves 21b and 22b are designed as throttle valves.
The control piston cylinder unit 34 comprises a pressure chamber 35, seals 36, and a ram 37, which is reset via a spring 38. A working piston 39 transfers the force. Pressure is built up via a solenoid valve 33a and reduced via a solenoid valve 40a. If a pressure regulator unit according to
The control piston cylinder unit 40 has a different design, since media separation exists. For braking systems in particular, media separation between the hydraulic circuit and the braking circuit is necessary. The control piston 43 therefore separates a pressure chamber 41 filled with hydraulic fluid and a second pressure chamber 42 (with brake fluid). The pressure chambers are separated via the control piston 43 and seal 44. In addition, a second expansion port seal 45 is provided, via which, when the piston is reset, brake fluid can be demanded from a further reservoir 46. The control piston transfers the pressure via a DMV valve to the front axle of the motor vehicle. A further pressure sensor 47 is provided for pressure control. Pressure build-up takes place via the valve 33b, and pressure reduction via valve 44b into the reservoir. As for consumer V3 this valve is omitted, if the pressure regulator unit according to
The braking system further contains an isolation valve TV, a path simulator, and a safety valve SiV. The braking system is connected via the isolation valve with a circuit 50 of the actuation unit of the pedal unit 49. The second circuit 51 is connected to the rear axle. Further pressure sensors 52, 53 and a path sensor 54 for the pedal travel are provided. Pressure regulation of the front axle in active mode is controlled via the path simulator. In the event of a fault (e.g. failure of the path simulator) the SiV is closed and the TV opened. In addition, the DMV valve is closed. The pedal force is then directly on the front axle. An ECU is also provided for the braking system, in which the valve control and evaluation of the pressure sensors takes place.
Leiber, Heinz, Leiber, Thomas, Unterfrauner, Valentin
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